This invention relates to laminar seed supports which are also known as laminar seed carriers or seed foils and to their preparation.
Laminar seed supports or carriers which consist of superimposed, mechanically united paper surfaces, between which seeds are, in practice, disposed with an irregular distribution are known. These seed carriers have the disadvantage that the plant development progresses in an irregular manner, since sometimes the plants are too close together and as a result an optimum growth of the plants is thereby impeded. Also the loose disposition of the seeds between the layers of paper, allow the seeds to be displaced during transport and handling, whereby the above disadvantages are increased.
The use of paper comprising long fibres also has the disadvantage in that during the germination of the plant the shoot and roots must grow through the paper layers and may therefore be impeded resulting in germination failures and/or retardation of growth.
It has been proposed to apply separate dots of adhesive substance at intervals to paper webs and to use these dots as points of adhesion for seed. When using this procedure, the seeds are dropped onto the paper surface which is moved upwardly and the seeds are retained only on those areas having the dots of adhesive substance. The disadvantage which arises in such a case is that several seed grains are able to stick side by side on any dots, resulting in an irregular and too close spacing of the plants. An additional disadvantage with this operating procedure is that, with the handling of the paper web, the seeds are able to break out as a consequence of the movement, and thereby failures occur.
Insofar as a size or adhesive substance is used according to the prior art for sticking the seeds to a support, the substances used have a slow water-solubility or are insoluble in water and accordingly the germination of seeds embedded within such substances is impeded as water is required for germination.
Seed supports which consist of paper quickly dry out after having been given a thin covering of soil when there is a lack of soil moisture, e.g. when there has been no rain, and the paper quickly regains the strength value existing in the dry state. In this state, the shoots and roots which develop during germination are unable to break through the paper. For a quick germination, it is particularly desirable to provide an extremely thin covering of soil or to omit providing any covering. The contact with the moist soil is consequently extremely restricted. After having been sprayed or after rain, the paper dries out quickly if the water capacity is too low.
German Patent Specification No. 79 129 discloses the production of a laminar seed carrier with super-imposed paper surfaces which are connected by adhesive bonding. According to this proposal, "a small amount of adhesive" is to be applied "to each position", which position "is to receive a seed grain" and "seeds are to be broadcast and trapped onto strips as thus provided with points of adhesion". It also states: "seeds then only remain adhering to the positions which carry adhesive". The statement is made that "when such seed strips are introduced into the soil, the natural or artificially applied moisture of the soil causes a decomposition or disintegration of the paper", so that "a germination of the seeds may occur". Therefore, according to this proposal, water is only to be imbibed into the paper by the moisture of the soil, so that a rapid disintegration of the strip is caused and therefore porous paper should be used as the support. Paper, however, only has a limited water capacity.
German Pat. No. 191,127 proposes the use of a seeding strip consisting of porous paper, such as blotting paper, with depressions for the positioning of the seeds and to stick these seeds in the depressions. German Patent No. 279,745 proposes using two paper layers consisting of fibrous material and to provide one of the layers with a "central line of adhesive material", to stick the seed grains on the said line and thereafter to stick the strips by lateral lines of adhesive.
German Patent No. 306,663 discloses the use of seed strips with perforations at regular intervals, through which the seed grains are drawn by suction. The paper strips are to be coated with rubber or size, so as to fix the seed grains thereon, and thereafter the covering paper is to be stuck thereon. German Patent No. 474,764 also proposes the use of absorbent materials and the use of dextrin as adhesive.
German Patent No. 826,516 is concerned with a method which uses a strip of unsized fibre paper, such as cellulose, cellophane, which "is automatically dissolved by the moisture in the soil". The "anchoring" of the seeds is to be effected by "being turned, folded or gummed therein" and thus this proposal uses only a single paper web.
German Offenlegungsschrift No. 2 164 536 relates to a method of seeding out seeds by means of a strip-like seed carrier which is able to rot away, to which carrier seeds are adhered by spots of adhesive. Paper, cellulose, rottable synthetic plastics material having troughs, are to be used as the support material.
German Offenlegungsschrift 2 150 770 relates to a "spread-out seed carpet" consisting of a base layer provided with binding agents, the seeds which are laid thereon and a covering layer disposed above the seeds. These layers consist of pressed peat, light-weight paper or similar cardboard qualities or of a rottable, porous material. Where the covering layer is not pressed on, without adhesive, an adhesive substance which is quick-drying and does not initiate any germination is to be used, concerning which, however, no details are given.
German Offenlegungsschrift No. 1 582 087 discloses a method in which the seed is bonded with a flat support, onto which is to be pressed a covering which fixes the seeds. The support and covering are to be formed in a substantially similar manner and are to consist of the same material. The seeds are intended to be introduced into depressions in the support. It is also possible for the seeds to be fixed by adhesive bonding. If this is the case, it is necessary to start with a preliminary treatment by which the seeds are made insensitive against a brief supply of moisture from the adhesive. This preliminary treatment consists in a drying procedure. The seeds are protected against moisture by a protective layer. No specific types of paper or adhesives are proposed.
German Offenlegungsschrift No. 1 757 655 relates to the packaging of seeds or seed supports in the form of strips or rolls of paper or similar material. The damaging effect of the adhesives on the seed is disclosed as being a disadvantage as is the use of crepe paper since such paper does not permit the passage of sufficient water and gases. This more recent proposal follows a different procedure. The seed supports are formed without using adhesives and the webs of paper-like material are united by crimping, stamping or heat-sealing in the form of dots or lines, which enclose the seeds. The paper webs are guided through rollers, one of which rollers carries the embossing pattern.
German Offenlegungsschrift No. 2 219 448 discloses a seed strip which, is a flexible, flat support, comprising blotting paper, which is able partially to rot away. A covering of a porous mat of synthetic plastics material is proposed whereby a mat of grown grass which can be rolled up may be produced. Starch paste is proposed as adhesive means.